luci-base: introduce luci.dispatcher.lookup()

The lookup function takes multiple, possibly malformed path fragments,
splits them on slashes, constructs a temporary path and looks up the
result in the dispatch tree.

If a matching node has been found, the function will return both the
node reference and the canonical url to it.

If no corresponding node is found, the function returns nil.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

modules/luci-base/luasrc/dispatcher.lua

@@ -658,6 +658,23 @@ function node(...)
 	return c
 end
 
+function lookup(...)
+	local i, path = nil, {}
+	for i = 1, select('#', ...) do
+		local name, arg = nil, tostring(select(i, ...))
+		for name in arg:gmatch("[^/]+") do
+			path[#path+1] = name
+		end
+	end
+
+	for i = #path, 1, -1 do
+		local node = context.treecache[table.concat(path, ".", 1, i)]
+		if node and (i == #path or node.leaf) then
+			return node, build_url(unpack(path))
+		end
+	end
+end
+
 function _create_node(path)
 	if #path == 0 then
 		return context.tree

modules/luci-base/luasrc/dispatcher.luadoc

@@ -116,8 +116,8 @@ Create a new dispatching node and define common parameters.
 
 ---[[
 Fetch or create a dispatching node without setting the target module or
-
 enabling the node.
+
 @class function
 @name get
 @param	...		Virtual path
@@ -133,6 +133,15 @@ Fetch or create a new dispatching node.
 @return			Dispatching tree node
 ]]
 
+---[[
+Lookup node in dispatching tree.
+
+@class function
+@name lookup
+@param  ...		Virtual path
+@return Node object, canonical url or nil if the path was not found.
+]]
+
 ---[[
 Alias the first (lowest order) page automatically